The present invention relates to a method of producing a joined body, with low-melting glass.
A large number of articles are formed from component parts by using a low-melting glass as a bonding material. An example of an article bonded with low-melting glass is an IC chip (a semiconductor device having an integrated circuit formed therein) mounted on a ceramic substrate sealed with a ceramic cap together with lead wires acting as external connection terminals. A particular type of such a package is termed a "cer-dip."
In order to produce such a cer-dip, first, lead wires are mounted on peripheral portions of a main surface of a ceramic substrate on which low-melting glass has been applied and baked. A conductive material (for example, a silver plated plate or the like) on which low-melting glass has been applied and baked is mounted in a recess in the ceramic substrate disposed to receive an IC chip. Thereafter, the low-melting glass is heated so that the conductive material and the lead wires are bonded to the ceramic substrate.
Thereafter, an IC chip is mounted on the conductive material by means of soldering, and wire-bonding is performed between the chip and the lead wires. Lastly, a ceramic cap on which the low-melting glass has been applied and baked is bonded to the ceramic substrate so as to seal the ceramic substrate to complete the process. FIG. 13 shows a flow chart of this process.
In such an article in which bonding is performed by heating baked low-melting glass, however, bubbles (voids in the glass) are generated in the low-melting glass during bonding.
The generation of such bubbles causes problems because they reduce the thermal conductivity between the silver plated plate and the ceramic substrate. This may cause defective soldering of the IC chip to the silver plated plate and, in addition, heat from the IC chip is not effectively conducted away from the package during use of the device. Furthermore, there is a risk of causing leakage in the cap seal between the ceramic substrate and the ceramic cap.
An object of the present invention is therefore to provide a method of producing a joined body through low-melting glass bonding in which bubbles generated during bonding by heating the low-melting glass can be reduced.